In the industrial processing sector, there is a need to separate the liquid component from the solid component of numerous mixtures. The efficiency of the processes available to perform this function decreases as the liquid content decreases. If the liquid content is less than 20% by weight, the processes and equipment available have a limited throughput. One object of this invention is to provide a process and equipment that will rapidly and effeciently separate liquids from liquid/solids mixtures in this region of operation.
Roller presses have been previously described to perform a de-liquifying function. U.S. Pat. No. 3,520,251 to Bodine describes a roller press having porous metal rollers through which the liquid passes into the interior, from which it is discharged. Kerr describes in U.S. Pat. No. 3,968,742, a similar arrangement. Both of these inventions use a unidirectional liquid flow (from the outer surface to the inner surface) that can also transport small particles of the solid material into the passageways in the rollers. This can cause the roller passageways to eventually become clogged, causing the liquid movement to be reduced. One object of this invention is to provide a reversing liquid flow: liquid flows from the mixture into the outer surface of the roller at the nip and is later forced back to the outer surface of the roller for removal. The reversing liquid flow provides a cleaning action to the passageways in the rollers to minimize clogging. Another object is to provide a filtration barrier between the mixture and the rollers to further reduce clogging. Also, the rollers rotate about bearings mounted on their endplates and are therefore subjected to bending stresses. This requires additional strength in the design of the roller, making them complex to construct and therefore expensive to produce. Another object of this invention is simplify the construction and reduce the cost. Further, the endplates effectively preclude access to the interior of the roller which limits the available methods for removal of the liquid. Another object of this invention is to eliminate the endplates and provide greater access to the interior of the rollers.